Scientific study of the interactions of an organism with its environment - determines organism’s distribution and abundance

Very broad field - ranges from adaptations of an organism to its environment to the dynamics of ecosystems

Traditionally a descriptive science - has increasingly become experimental

Abiotic factors - nonliving - e.g., temperature, sunlight, water, substrate, periodic disturbances (weather)

Biotic factors - living - e.g., food types and availability, disease & predators, effects of crowding and competition

Organism - individual of a given species

Population - group of individuals of same species in a given area

Community - group of populations that actually or potentially interact

Ecosystem - biotic and abiotic elements

Biome - major community (e.g., savannah)

Biosphere - totality of all ecosystems

Individual composed of cells that are organized into tissues, organs and organ systems

Organismal ecology - concerned with morphological, physiological and behavioral adaptations that allow organism to function in presence of biotic and abiotic elements of environment

Population - group of individuals of same species in a given geographic area

Note: sexually-reproducing species defined as "actually or potentially interbreeding individuals that are reproductively isolated from other such groups"- a shared gene pool

Population ecology - concentrates on factors affecting the distribution and abundance of population(s)

Community - all individuals of all species that inhabit a given area - biotic elements

Community ecology - deals with interactions among species within community

Ecosystem - totality of biotic and abiotic elements interacting within a given geographic area

Ecosystem ecology - emphasis on energy flow and cycling of chemicals among biotic and abiotic elements of ecosystem

Landscape (or Seascape) - two or more ecosystems linked by exchanges of energy, materials and organisms

Landscape ecology - focuses on how arrays of ecosystems are arranged and interact in geographic region - e.g., how components in aquatic ecosystems are affected by logging practices

Biome - major ecosystem over extremely large area - typically classified according to predominant vegetation - e.g., grassland

Biosphere - the global ecosystem - sum of all of planet’s ecosystem

Account for largest part of biosphere in terms of area - e.g., marine biomes cover 75% of earth’s surface

Enormous effect on biosphere - evaporation of seawater accounts for most precipitation - algae & photosynthetic bacteria supply most of earth’s oxygen - major sink for carbon dioxide

Most exhibit vertical stratification of physical and chemical variables

Light penetration - in photic zone light intensity sufficient for photosynthesis - intensity insufficient in aphotic zone (no photosynthesis)

Temperature profiles - may vary seasonally - typically stratified during warmer periods - layers may be separated by distinct thermocline - mixing and uniform temperature profile may occur during spring and fall turnovers

Both factors influence distribution of aquatic organisms

Two general categories - moving water (rivers & streams) and standing water (ponds & lakes) -

Stratification and zonation usually evident in both - biological communities unique

Littoral zone - close to shore - shallow, well-lit - plants inhabit bottom (benthic zone)

Limnetic zone - farther from shore - open surface waters - inhabited by phytoplankton & algae - no plants on bottom in profundal (aphotic) zone

Benthic zone - bottom - photic and aphotic

Distinct communities in each zone

Oligotrophic - typically deep, nutrient-poor and relatively nonproductive (phytoplankton & algae sparse)

Eutrophic - typically shallower, nutrient-rich and productive (phytoplankton, algae & plants abundant - may be accelerated by pollution (phosphates, etc.) - leads to aging and "death" of standing water bodies

Mesotrophic - intermediate

Intertidal zone - periodic immersion followed by exposure - determined by tidal flow - harsh

Neritic zone - relatively shallow water - extends to continental shelf

Oceanic zone - deep water beyond continental shelf - palagic zone extends from surface to bottom - includes both photic and aphotic zones

Distinct biological communities within each stratum

Geographic distribution of terrestrial biomes based mainly on regional variations in climate

Terrestrial biomes generally named for major physical-climatic features and for dominant vegetation (e.g., tropical rain forest, temperate grasslands)

Vertical stratification important - e.g., forest floor, understory, canopy, etc.

Study of past and present distribution of individual species and groups

Involves both evolutionary history and current factors limiting distribution of species and groups

Had major impact on Darwin’s ideas on evolution

Earth’s major regions - characterized by distinctive floras and faunas

Result of continental drift and barriers to dispersal

Not sharply delineated - intergrade at boundaries

Potential range - geographic area potentially inhabitable by organisms

Actual range - range actually inhabited - is typically smaller than potential range

Discrepencies due to limiting factors

Most species have small geographic ranges

Evolutionary history - effects of continental drift

Abiotic factors - chemical and physical factors - e.g., water availability, climate, temperature

Biotic factors - predation, parasitism (including disease), competition

Dispersal - area may be inaccessible or time to colonize may be insufficient

Behavior - suitability of area or habitat

Climate - prevailing weather conditions at a locality (long-term trends) - temperature, water availability, light & wind

Climate different from weather (short-term perturbations in temperature, precipitation, etc.

Sets overall framework within which organism(s) must function - sets major constraints on survival and reproduction

Earth has periodically undergone climatic changes

Currently experiencing global warming - accelerated by increases in carbon dioxide levels - affected by burning of fossil fuels

Climatic change profoundly affects geographic distribution of biological organisms - those not adapted to changes commonly decline to extinction